We still have a legacy network of about 50 machines running vanilla XP. 95% of my time is spent dealing with C2K issues, legacy network runs very well, although probably not used as much as the C2k system.
We're due a new school, I don't know what way they'll jump - I know our Technology department would like their own system, as would Science and Music. Storage space and software problems have always been the issue with the C2K system, if they could sort these out it would help a great deal.